The mild and relatively dry weather made any last minute errands easy but the crowds were another story.

But in general, the holiday shopping season is losing some of its power in the year's sales.

November and December now account for less than 21 percent of annual retail sales at physical stores, down from a peak of over 25 percent, and experts believe it'll keep dropping. Those extra percentage points would have translated into an extra $70 billion more in buying for last year, says Michael Niemira, principal at The Retail Economist.

The season had steadily gained in importance and peaked in the early '80s, before the dominance of big discounters like Wal-Mart stalled its growth as shoppers began moving away from department stores. Still, the two-month period held its own through the mid-'90s, when online shopping for deals took hold.

"There was a mindset even before online shopping," said Niemira, whose data goes back to 1967. "But this just accelerated it."

In general, many people are shopping for the holidays all year long now, mirroring the trend for back-to-school items. Heavy discounting has diluted sales, and with big promotions throughout the year, shoppers no longer hold off making their biggest purchases until the holidays.